This invention relates to processes designed to treat mono ethylene glycol (“MEG”) used in the oil and gas industry to control hydrates formation. More particularly, the invention relates to MEG reclamation processes which are designed to remove salts from a wet MEG feed stream.
In the oil and gas industry, dry (lean) MEG is used to control the formation of hydrates within a produced stream. Once used, the now wet (rich) MEG is, in turn, dried and cleaned by way of a MEG regeneration and reclamation process so the MEG can be used again in hydrate control. The systems and methods used to recover MEG usually include three sections: pre-treatment, flash separation, and MEG regeneration. These sections can be followed by salt management and followed or preceded by a calcium removal section.
The MEG used for hydrate inhibition in natural gas pipelines has a similar volatility to organic acids such as acetic acid. Therefore, if water from a well contains organic acids, the organic acid tends to stay with the MEG solution. Removing this organic acid can require large, costly and wasteful blowdown or purges of MEG.
Other options for the removal of organic acid from rich MEG include boiling off the organic acids, distillation of the rich MEG and organic acid, and precipitation using divalent cations. The boiling off method requires a relatively large heating duty to heat the whole stream and/or vacuum conditions. Because the relative volatilities of MEG and organic acid are similar this method also produces large MEG losses. The distillation method, similar to the boiling off method, requires a large heating (reboiling) and cooling (condensing) duty. Although the MEG losses are reduced by distillation, more equipment is required (e.g., column, reboiler, condenser). The precipitation method requires the addition of chemicals to increase the pH and a solid separation step such as centrifuge or filtration (see e.g. US 2015/0119609 A1).